“Cracks” is the screen adaptation of a 1999 novel by Sheila Kohler (“Becoming Jane Eyre”), set in a South African boarding school in the 1960s. The screenplay, by Caroline Court and Ben Ip, moves the story to the fictional Stanley Island, a desolate retreat off the coast of England, and pushes the period back to 1934.

The movie’s house of mischief, St. Mathilda’s School, is an imposing edifice only somewhat less forbidding than the Ashecliffe Hospital for the criminally insane in “Shutter Island.” It is not a place you would ever describe as homey. And because only a ferry connects it to the mainland, you have an uneasy sense that the residents, for all their privilege, are prisoners in a madhouse presided over by prim, icy matrons determined to protect the school’s reputation at all costs.

The story fixes on the elite diving team, a tightly knit group of girls of varying ages who through much of the film seem to be the only students in the entire institution. It is one of many bizarre touches that takes “Cracks” into the realm of the surreal. Late in the movie we learn that the team is an ingrown little clique that for unexplained reasons never competes with other schools.

Watching over them with a hawklike possessiveness and pride is their coach, Miss G (Eva Green), a glamorous, dark-eyed beauty whom the girls idolize as she regales them with fishy-sounding tales of her world travels. Early in the film she delivers a stirring declaration that feels somewhat unhinged: “The most important thing in life is desire.”

The team captain, Di (Juno Temple, in a taut, increasingly scary performance), is fiercely protective of her status as teacher’s pet and ranking alpha girl. Trouble begins with the arrival of a new student, Fiamma (María Valverde), a sultry beauty who has superior diving skills along with a calm worldliness that none of her teammates possess.

From an aristocratic Spanish background, Fiamma is an independent spirit who doesn’t struggle to fit in with the group and seems more or less immune to its members’ hostility when they turn on her. Mysterious and detached, she comports herself with a certain hauteur and lets it be known that she is only biding her time at a place she doesn’t want to be.

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The hierarchy is shaken the moment Fiamma climbs the diving tower and executes a perfect somersault that raises the bar for the entire team and leaves Miss G dumbstruck with admiration. But Fiamma is indifferent when Miss G adopts her as her new favorite and pursues an intimate friendship with an increasingly reckless abandon. Fiamma’s fate as an outcast is sealed when Di, consumed with jealousy, enlists the other team members in a campaign to drive her out of the school.

“Cracks” is a small story writ very large. With its shadowy interiors and shots of faces in the grip of obsession, it verges on a horror film. The demonic forces explode during a party at which Fiamma passes out after drinking too much wine.

As the story progresses, Ms. Green’s teacher, an avid chain smoker, becomes steadily more unbalanced. Her performance follows the same arc as Glenn Close’s in “Fatal Attraction” but draws short of total monstrosity. You feel her pain as her unrequited passion for Fiamma drives her to make a horrifying, spur-of-the-moment choice.

In many ways “Cracks” is lurid and rickety. But its gripping ensemble performances lend it an emotional intensity that outweighs its shortcomings.

CRACKS

Opens on Friday in Manhattan.

Directed by Jordan Scott; written by Caroline Court and Ben Ip, based on the novel by Sheila Kohler; director of photography, John Mathieson; production design by Ben Scott; costumes by Allison Byrne; produced by Kwesi Dickson, Julie Payne, Andrew Lowe, Christine Vachon and Rosalie Swedlin; released by IFC Films. Running time: 1 hour 47 minutes. This film is not rated.

A version of this review appears in print on March 18, 2011, on Page C11 of the New York edition with the headline: At Desolate Girls’ School, Diving Teacher Rules Roost. Order Reprints|Today's Paper|Subscribe